Generally, various processes such as film formation, etching, oxidation, diffusion and the like are performed on a wafer to manufacture a semiconductor integrated circuit. For example, Japanese Patent Application Publication No. 2000-208589 discloses a processing system in which a plurality of processing apparatuses for performing the same process or different processes is connected to one another through a common transfer chamber in order to improve a throughput and a yield along with the trend toward miniaturization and high integration of the semiconductor integrated circuit.
In such a processing system, a semiconductor wafer is unloaded from a container installed at an inlet port which is provided at, e.g., a front stage of the processing system, and loaded into the transfer chamber of the processing system by using a transfer unit. Then, the wafer is sequentially introduced into the respective processing apparatuses from the transfer chamber connected to the processing apparatuses to be subjected to consecutive processes. Further, the processed wafer is accommodated in the original container through, e.g., the original path.
Meanwhile, as described above, such a processing system has therein a single or a plurality of transfer units, and the transfer of the wafer is automatically performed by the transfer units.
The transfer unit has one or two picks capable of contracting/extending, rotating and vertically moving, for example. The wafer is moved to a transfer position and transferred to a predetermined position while being directly held by the pick. In this case, the pick of the transfer unit or the wafer held by the pick should be protected from interference or collision with another member while the pick is moving to receive or deliver the wafer. In addition, it is required to hold the wafer at a specific position, move the wafer to a desired position, and transfer the wafer to an appropriate position with high precision, e.g., ±0.20 mm or less.
Therefore, when an apparatus is assembled, subjected to large modification or the like, there is performed a positioning method, i.e., a so-called teaching operation, which stores an important position such as the location where the wafer W is transferred on a moving route of the pick of the transfer unit, as transfer position coordinates, in a control unit such as a computer or the like for controlling the operation of the transfer unit.
The teaching for each pick is performed at almost every location where the wafer is transferred, i.e., a location (point) accessed by the pick, such as positional relationships between the transfer unit and the container, between the support unit of the load-lock chamber and the pick, between the pick and the position alignment unit, and between the pick and the susceptor of each of the processing apparatuses. Further, the transfer position coordinates are stored. Every driving system has an encoder for specifying a driving position, and the moving amount can be controlled with high precision by controlling the number of pulses of, e.g., a pulse motor or the like.
In a conventional teaching method, a semiconductor wafer is precisely disposed at a transfer location by an operator and is brought into contact with a pick of a transfer unit by the operator who is checking the semiconductor wafer and the pick with naked eyes. The coordinates on the horizontal plane, the height position or the like at that time are stored as the reference and, then, the pick is automatically driven based on the stored coordinates.
As for another positioning method, there is known a teaching method for calculating an access height to each unit by detecting a height position of a teaching jig by a mapping sensor provided at a leading end of a transfer arm, as described in Japanese Patent Application Publication No. 2006-185960. As for still another positioning method, there is known a teaching method for calculating a position, an angle direction or the like of an object by accessing a feature body having a geometric relationship with the object three times by using a beam detector provided at a leading end of a driving arm, as described in Japanese Patent Laid-open Publication No. 2009-506518 (particularly, claim 39 and the like).
In the above positioning method, since the mounting pad is brought into contact with a backside of the wafer W, it is difficult to check the contact state with naked eyes and deviation between operators is large.
In order to install a wafer at a teaching position, a ceiling cover of the apparatus which corresponds to the teaching position needs to be opened, which may operation efficiency deteriorates. In JP2006-185960A, a Z-axis (vertical direction) teaching jig is additionally required, which is troublesome. In JP2009-506518A, a beam detector provided at a pick is made to access, e.g., three substrate support pins, and a position or a direction of a substrate station in a horizontal plane is obtained (see, paragraphs 0030 and 0031). Further, when the pick is made to access each of the substrate support pins, an operator should perform the access operation with naked eyes and a working efficiency deteriorates.